This invention relates to a process for catalytically hydrogenating sulfolenes to sulfolanes. In another aspect, this invention relates to a process for hydrogenating sulfolenes to sulfolanes over a nickel catalyst. In a further aspect, this invention relates to pretreating sulfolenes so as to remove impurities, particularly SO.sub.2, which interfere with the subsequent catalytic hydrogenation of sulfolenes.
The catalytic hydrogenation of sulfolenes to sulfolanes is well known. Generally a supported nickel catalyst is employed. Also the removal of sulfur dioxide and other impurities from sulfolenes by means of oxidizing agents has been disclosed, e.g., in U.S. Pat. Nos. 3,622,958; 3,514,469; 3,417,103 and 3,152,144. However, there is an ever present need to find still more effective methods of removing impurities from sulfolenes so as to speed up the subsequent hydrogenation of sulfolenes to sulfolanes and to reduce the amount of catalyst used.